1. EECE.2160 ECE Application Programming
Instructor:
Dr. Michael Geiger & Dr. Lin Li
Spring 2019
Lecture 18:
Functions

2. ECE Application Programming: Lecture 18
Lecture outline
Announcements/reminders
Program 4 due 3/21
Exam 2: Monday, April 1
Today’s lecture
Review: Functions
Function examples
4/6/2019
ECE Application Programming: Lecture 18

3. ECE Application Programming: Lecture 18
Review: functions
Used to break programs into smaller pieces
Useful when code sequences repeated
Functions have:
An optional return value
A name
Optional arguments
Must be prototyped or written completely prior to use
Preferred method: prototypes in header file, function definitions in one source file, main function in separate source file
We’ve discussed arguments passed by value:
Copy of argument is sent to function
Arguments cannot be modified outside function
4/6/2019
ECE Application Programming: Lecture 18

4. ECE Application Programming: Lecture 18
Example
What does the following print?
int f(int a, int b);
int main() {
int x = 1;
int y = 2;
int result1, result2, result3;
result1 = f(x, y);
result2 = f(y, result1);
result3 = f(result1, result2);
printf("x = %d, y = %d\n", x, y);
printf("Result 1: %d\n", result1);
printf("Result 2: %d\n", result2);
printf("Result 3: %d\n", result3);
return 0; }
int f(int a, int b) { int i; // Loop index int r = 0; // Result for (i = 0; i < a; i++) r += b; return r; }
4/6/2019
ECE Application Programming: Lecture 18

5. ECE Application Programming: Lecture 18
Example solution
x = 1, y = 2 Result 1: 2 Result 2: 4 Result 3: 8
4/6/2019
ECE Application Programming: Lecture 18

6. Example: Writing functions
Write a function that:
Takes an integer, length, as an argument and prints a series of “length” dashes on a single line
Reads an integer value from the console input and returns 1 if the value is even, 0 if it’s odd
Takes four double-precision numbers as arguments and returns their average
4/6/2019
ECE Application Programming: Lecture 18

7. ECE Application Programming: Lecture 18
Example solutions
Write a function that: Takes an integer, length, as an argument and prints a series of “length” dashes on a single line
void printLine(int length) {
int i;
for (i = 0; i < length; i++)
printf(“-”); }
4/6/2019
ECE Application Programming: Lecture 18

8. Example solutions (cont.)
Write a function that: reads an integer value from the console input and returns 1 if the value is even, 0 if it’s odd
int checkEvenOdd() {
int value;
scanf(“%d”, &value);
if ((value % 2) == 0)
return 1;
else
return 0; }
4/6/2019
ECE Application Programming: Lecture 18

9. Example solutions (cont)
Write a function that: takes four double-precision numbers as arguments and returns their average
double avgFour(double a, double b,
double c, double d) {
return (a + b + c + d) / 4.0; }
4/6/2019
ECE Application Programming: Lecture 18

10. ECE Application Programming: Lecture 18
Final notes
Next time
More function examples (Monday, 3/18)
Enjoy your Spring Break!
Reminders:
Program 4 due 3/21
Exam 2: Monday, April 1
4/6/2019
ECE Application Programming: Lecture 18